In general, a polyurethane foam is obtained by reacting a resin premix which is prepared from a polyol, a catalyst for preparation of a polyurethane foam, a foaming agent, etc. with a polyisocyanate.
The polyurethane foam is widely used as an insulating material in electric refrigerators, freezers, cold storage warehouses, construction panels, etc. due to its superior insulating performance, moldability and self-adhesivity and in automobile interior parts such as seat cushions, seat backs, head rests, arm rests, instrument panels, door trims, ceiling materials, etc., saddles of motorcycles, seats for airplanes and trains and cushioning materials of furniture, bedding, chairs, etc. due to superior cushioning property.
In general, a petroleum-based synthetic polyol is mainly used for the preparation of a urethane foam. There have been many efforts to prepare ecofriendly polyurethanes by replacing the petroleum-based polyol with a vegetable oil-based natural polyol (Petrovic, Z. S., “Polyurethanes from Vegetable Oils,” Polym. Rev., 48(1), 109-155 (2008); Kong, X., and Narine, S. S., “Physical Properties of Polyurethane Plastic Sheets Produced from Polyols from Canola Oil,” Biomacromolecules, 8(7), 2203-2209 (2007); etc.). However, the urethane foams prepared from vegetable oils are mostly hard urethane foams and preparation of soft urethane foams using vegetable oils have not been studied enough. Although synthesis of soft foams only from a soybean oil-based polyol was reported, a lot of closed cells were observed (J. John, M. Bhattacharya, and R. B. Turner, Characterization of polyurethane foams from soybean oil, J. Appl. Polym. Sci., 86, 3097 (2002).)
The soft polyurethane foam is utilized in various industrial applications such as packaging due to superior elasticity and mechanical strength (elongation, tensile strength and wear resistance) owing to its open cell structure.
Recently, as cosmetic products in which a cosmetic composition is impregnated in a urethane foam, such as cushion pacts, cushion cosmetics, are appraised as revolutionary products, interests in the soft urethane foam are increasing in the cosmetic product industry.
The urethane foam which is prepared from a polyol, a multifunctional isocyanate, a foaming agent, etc. may have various properties depending on the polyol. A soft urethane foam sponge is prepared from a polyol with a relatively large molecular weight. Polyether- and polyester-based polyols are mainly used.
As a urethane foam for impregnating a cosmetic composition, the ether-type polyurethane foam is usually used. However, the ether-type polyurethane foam is disadvantageous in terms of tensile strength, hardness, elongation and flame retardancy as compared to the ester-type polyurethane using a polyol containing ester linkages. The ester-type polyurethane foam has a uniform cell structure and is resistant against oxidation due to superior chemical resistance. However, it is known to have weak water resistance because it is hydrolyzed unlike the ether-type polyurethane foam. For this reason, its use for impregnating a cosmetic composition is extremely limited.
There have been efforts to select a suitable urethane foam impregnating material by mixing an ether-based polyol with an ester-based polyol according to the physical properties and ingredients of a cosmetic composition. However, there is a problems in that the polyols do not have good compatibility.
Although polarity can be controlled to some extent by controlling the compositional ratio of the isocyanate and other additives used in the preparation of the polyurethane foam, there is a limitation in controlling the polarity variously according to the physical properties of the cosmetic composition.